Spectacle-glass.



B. M. HANNA, SPECTACLE GLASS. )APPLIOATIOH FILED 1,111.29, 1914.

Patented July 21, 19M

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M- W 7%. JM W w BENJAMIN M. HANNA, 0E rrr'rsnuaen, PENNSYLVANIA.

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Specification of Letters Patent.

Patented July 21.; 11914..

Application filed January 29, 1914. Serial No. 815,125.

To all wh0m it may concern Be it known that I, BENJAMIN M. HANNA, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, a

citizen of the United States, have invented or discovered certain new and useful Improvements in Spectacle-Glasses, of which improvements the following is a specification.

My invention relates to improvements in bi-focal eye-glasses, and the object of my improvement'is to overcome certain objectionable features which these glasses as they are now constructed possess.

The invention is illustrated in the accompanying drawings.

Figures 1 and 2 show in side elevation and in vertical medial section on larger scale a bi-focal eyeglass formed in the manner now generally employed. These two figures are introduced for purposes of comparison with the remaining figures which illustrate my invention. Figs. 3, 6, and 7 show in side elevation and with variation in detail eyeglasses embodying my invention, and Figs. 4: and 5 show the glass in vertical medial section and on larger scale. Three alternate forms in elevation are shown and two alternates in section; and it is to be understood that either of the sectional alternates is applicable to any one of the three elevation alternates. Fig. 8 is a digrammatic illustration to which a passage in the ensuing description particularly refers. Figs. 9, l0, and 11 are three sectional views corresponding to Fig. 4:, but on much larger scale, and illustrating more minute permissible variations in detail. Fig. 12 is a view corresponding to Figs. 3, 6, and 7, and illustrates a further variation in detail of construction.

In bi-focal spectacle glasses, it is desirable to have the largest possible area of the secondary or reading lens, for downward vision, and at the same time to intrude as little as may be upon the area of the primary or distance lens, for level vision. Consequently the secondary or reading lens is ordinarily arranged in the lower portion of the spectacle glass andis in plan of the lenticular shape, shown in Fig. 1 of the accompanying drawings-the lower edge a conforming to the lower margin of the glassand the upper edge I; convex. y

The met 0d now ordinarily employed in making these spectacle glasses is to apply the lens 2 against the face of the body 1,

uniting the parts by cement, ordinarily Canada balsam. This is indicated in Fig. 2

of the drawings (a section on the line II- II, Fig. 1), in which the surfaces of union by cement are indicated by the line 0. Cement changes in time and: service, to the impairment of the optical properties of the glass, and is for that reason undesirable.

My invention is directed'to avoidance of the necessity of using cement over the surfaces through which vision. is gained.

In a co-pending application, filed December 23, 1913, Serial No. 808,497, I have described and' claimed a method of uniting bodies of glass while in solid state, and have described it as serviceable in making bifocal eyeglasses. The method involves an application of] the principles of thermal expansion.

My present invention has to do with the shaping of: the component parts of lo i-focal eyeglasses, and is, in part, disclosed in the application referred to.

In the practice of my present invention, I recess the main body of the spectacle glass for the reception of the reading lens; and this recess may extend through the main body (Fig. 5) or may be superficial, upon one face of the main body (Fi l); and I secure the reading lens. withi-nt is recess by an edgato-edge engagement only, thus avoiding the necessity 0t using a cement oven surfaces through which vision is to be had.

If I were to attempt.- to fiorm within the main body a recess (.whether superficial or extending through) for the inserted reading lens of the s ape in planv shown in Fig. 1, I would be unable to get security of union by any edge-to-edge engagement known to me. Cement would not, with such a shape, be adequate; the shocks incident to use would soon loosen the reading lens and it would fall out. But when I adopt either of the shapes shown in. Figs. 7 and 8 of the ap- ,and dust from between the lens faces.

plication referred to (Figs. 8 and 6 of this application), I may then unite the components, either by the differential heat method described in that other application, or by the use of cement or other filling material along the .edges only, or by both means, and obtain a union secure for service.

Referring first to Figs. 3 and 6, it will be observed that the upper edge of the secondary lens, instead of being formed of simple divergent curvature, as shown in Fig. 1, is formed with a slight convergence of curvature, which may be at the periphery, as illustrated at w, m, Fig. 3, or at intermediate points, as illustrated at y, y, Fig. 6. In these cases the secondary lens member may be .Sefin a superficial recess prepared for it in the body of the primary lens member, as indicated in Fig. 4, 'or mayv occupy the whole thickness of the s ectacle glass, as in dicated in Fig. 5. As as been intimated,-

the relative dimensions of the recess and of I the secondary lens which is inserted within cement or other filling material along the edges; or the relative dimensions may be such as torequire the .application of such material to the edges. The application of cement or other material may extend all the way around the engaging edges or part way, as desired. The presence of such material at the edge, asidefromits value if any as an adhesive, is useful to exclude moisture The secondary or reading lens 2 may be inserted in its recess either in a direction transverse to the face of the glass, or (the overhanging points formed by convergent curvature at w and 3 Figs. 3 and 6, bemg of proper size and the relative dimensions permitting) the secondary lens 2 may be. inserted in an edge- Wisc direction, a. e. parallel with the general plane of the glass.

My prese t application in its broadest aspect is not owever limited to the shaping of the meeting edges of the lens parts with portions of convergin curvature.- This will be apparent on consi eration of 7 and the diagrammatic showin of Fig. 8. The dotted lines I) of Fig. 8 il ustrate the usual contour (see Fig. -1) my improvement lies in breaking this contour line, and forming the contour with the'opposing, and in this case parallel, lines z z. In this case, let it be imagined that a strain is exerted (the ar of a fall, for instance), tending toseparate the components, and acting in the dlrection indicated by the .arrow 70. In case the contour is as usual (indicated at b) the strain is unopposed, and if sufficiently severe..w1ll cause theinserted secondary lens 2 to break away from the containing body 1; but, in the case of the contour of my invention, the strain is opposed by the bearing along edge 2,- and, unless increased very much beyond that suflicient to cause separation in the other case, the union will be secure.

The latitude of permissible variation in detail of structure is further indicated in Fig. 12; the main body and the insert may be keyed together and the particular dispo sition of the key may be such as is preferred. In Fig. 12 it appears that a recess may be formed inthe edges of contact extending into the body 1 on one side and the insert 2 on the other, and into this recess a key 3 may be let, and this key will be effective to hold the component parts of the eyeglass against separation. Stated in other words, and in view of the variations now explained, my invention consists in a certain shaping of the arts; and it will be observed that in each il ustration there are surfaces designed to resist and overcome oblique strains tend- .ing to separate the component lenses of the spectacle glass. And it will be noted in this connection that the oblique strains thus guarded against are more effective to cause separation (if not guarded a ainst) than vertical strains-a. e. parallel with the edges 2'2 of Fig. 8.

Figs. 9, 10, and 11' are intended to show that the meeting edges of insert and recess may be shaped variously, as indicated at m, a, o. The form shown at 0 if made flaring to amarked degree, would not be effective to afford union by the differential vtemperature method of the application referred to, but would require the application of cement to the meeting edges. The shape indicated in Fig. 9, wherein the insert 2 is held in the body 1 against lateral displacement by the 'overhangin rim of the edge m of the recess is pre erred. This .overhangin rim will be effective whether engaging t e'inserted lens directly, or indirectly through a body of cement or other material, to increase the security of such insert. This feature is effective, regardless of the particular position of the insert within the main body of the glassc'. 6. whether or not it be marginal.

I claim as my invention:

1. In .'a='bi-focal eyeglass,- the combination of a primary lens having a marginal recess and a secondary lens inserted in such recess, the edges of such recess being in the main divergent toward the margin but their divergence =being interrupted and the interruption affording surfaces opposed to oblique strains tending to separation of the secondary lens when in place in thesaid recess of the primary lens.

2. A bi-focal eyeglass in which the normal body and insert is broken by an irregularity and a secondary lens inserted in such recess, affording surfaces opposed to oblique strains the edges of such recess being interrupted I tending to separation. by overhanging points.

' 3. In a bifocal eyeglass, the combination In testimony whereof I have hereunto set 5 of 3 primary lens, and a seconcllary kilns carmy hand.

rie in a recess in t e primary ens, t e edge of the recess in the primary lens being BENJAMIN HANNA formed with an overhanging rim. Witnesses:

4. In a bi-focal eyeglass, the combination BAYARD H. CHRIsTY,

10 of a primary lens having a marginal recess FRANoIs J. TOMASSON. 

